1. Field of the Invention
The present general inventive concept relates to an image forming apparatus including a fuser having two or more different rated voltages and a method of controlling a fusing temperature of the same.
2. Description of the Related Art
An image forming apparatus forms an image according to processes as described below. First, an electrostatic latent image is formed by exposing a photosensitive body, and the electrostatic latent image is developed by supplying toner thereto. In other words, toner particles charged on a surface of the photosensitive body are distributed according to a shape of the electrostatic latent image. Next, the image formed on the photosensitive body is transferred onto a printing medium. In other words, toner particles on the surface of the photosensitive body are transferred onto the printing medium. Finally, a toner image formed on the printing medium is fused to the printing medium by heating and pressing the toner image. Then, the image forming processes are completed.
Among the image forming processes, the process of fusing a toner image formed on a printing medium will be described below in detail. The printing medium on which the toner image is formed is carried into a fuser consisting of a heating roller and a pressing roller and fusion is performed thereon. The heating roller may include a heat generating body and may be heated by heat generated by the heat generating body, whereas the pressing roller forms a fusing nip with the heating roller by contacting at a certain point. The printing medium is heated and pressed by the heating roller and the pressing roller as the printing medium passes through the fusing nip of the fuser, and thus the toner image is fused. The heat generating body is supplied with power and generates resistance heat and may generally include a halogen lamp, for example.
Recently, image forming apparatuses having two or more different rated voltages are widely manufactured. To embody an image forming apparatus having two or more different rated voltages (hereinafter, referred to as a “free voltage image forming apparatus”), a fuser included therein should also be a fuser having two or more different rated voltages (hereinafter, referred to as a “free voltage fuser”). However, a heat generating body included in a fuser has a resistance value set to receive a desired level of power with respect to an input voltage. Therefore, to embody a free voltage fuser, the free voltage fuser may include a plurality of heat generating bodies having their own resistance values respectively corresponding to rated voltages. Alternatively, the free voltage fuser may include a single heat generating body and desired powers may be acquired by controlling a supply of fusing power.
In a case where a fuser includes a plurality of heat generating bodies having resistance values respectively corresponding to rated voltages, there are problems including increased manufacturing costs, an increased size, an increased weight, etc. In a case where a fuser includes a single heat generating body and free voltage is embodied by controlling fusing power supplied to the fuser, an inrush current and a flicker may occur during application of a relatively high rated voltage from among a plurality of rated voltages of an image forming apparatus. The main reason that the inrush current and the flicker occur is related to a positive temperature coefficient (PTC) characteristic of a halogen lamp used as a heat generating body of a fuser. Due to the PTC characteristic, a halogen lamp has a low resistance at low temperatures, and a resistance of the halogen lamp increases as the temperature increases. Therefore, when a halogen lamp is initially driven, fusing power is input when the resistance of the halogen lamp is low, and thus the inrush current and the flicker occur.